If you're lucky 20 minutes. That night train leaves from track number 10 and the previous train from that track leaves at 20:00. But don't be surprised if it's only 10 or even 5 minutes. Amsterdam Centraal is a very busy station and doesn't have a lot of capacity to spare.

Usually just 10minutes as there is not much Capacity on the tracks arround Amsterdam Central :/ 

Good to know thanks very much both. Assume we can use first class lounge with first class pass here?

In Amsterdam yes and Vienna yes :) Keep in mind the Lounge in Amsterdam closes pretty early :/ 

However not all 1st class lounges accept 1st class Railpass user (eg. Germany or Italy) but Amsterdam & Vienna are fine :) 

Austrian lounges and the Lounge in Budapest Keleti are one of the best for Railpass user :)